Fasting metabolic movements

Bio luminescent methods provide researchers with unique opportunities to track growth and movement of cells in real-time and to non-destructively monitor fast metabolic changes with high sensitivity and specificity directly in a live animal or cell.10 13 Despite these evident advantages, few results have been reported on the application of bioluminescent methods for monitoring the processes of bacterial infection."... 

FIGURE 28-5 Schematic illustration of the movement of cytoskeletal elements in slow axonal transport. Slow axonal transport represents the movement of cytoplasmic constituents including cytoskeletal elements and soluble enzymes of intermediary metabolism at rates of 0.2-2 mm/day which are at least two orders of magnitude slower than those observed in fast axonal transport. As proposed in the structural hypothesis and supported by experimental evidence, cytoskeletal components are believed to be transported down the axon in their polymeric forms, not as individual subunit polypeptides. Cytoskeletal polypeptides are translated on cytoplasmic polysomes and then are assembled into polymers prior to transport down the axon in the anterograde direction. In contrast to fast axonal transport, no constituents of slow transport appear to be transported in the retrograde direction. Although the polypeptide composition of slow axonal transport has been extensively characterized, the motor molecule(s) responsible for the movement of these cytoplasmic constituents has not yet been identified. 

Cytoplasmic and cytoskeletal elements move coherently at slow transport rates. Two major rate components have been described for slow axonal transport, representing movement of cytoplasmic constituents including cytoskeletal elements and soluble enzymes of intermediary metabolism [3]. Cytoplasmic and cytoskeletal elements in axonal transport move with rates at least two orders of magnitude slower than fast transport. 

The cytosol is the fluid compartment of the cell and contains the enzymes responsible for cellular metabolism together with free ribosomes concerned with local protein synthesis. In addition to these structures which are common to all cell types, the neuron also contains specific organelles which are unique to the nervous system. For example, the neuronal skeleton is responsible for monitoring the shape of the neuron. This is composed of several fibrous proteins that strengthen the axonal process and provide a structure for the location of specific membrane proteins. The axonal cytoskeleton has been divided into the internal cytoskeleton, which consists of microtubules linked to filaments along the length of the axon, which provides a track for the movement of vesicular material by fast axonal transport, and the cortical cytoskeleton. 

Individuals with either type of diabetes are unable to take up glucose efficiently from the blood recall that insulin triggers the movement of GLUT4 glucose transporters to the plasma membrane of muscle and adipose tissue (see Fig. 12-8). Another characteristic metabolic change in diabetes is excessive but incomplete oxidation of fatty acids in the liver. The acetyl-CoA produced by JS oxidation cannot be completely oxidized by the citric acid cycle, because the high [NADH]/[NAD+] ratio produced by JS oxidation inhibits the cycle (recall that three steps convert NAD+ to NADH). Accumulation of acetyl-CoA leads to overproduction of the ketone bodies acetoacetate and /3-hydroxybutyrate, which cannot be used by extrahepatic tissues as fast as they are made in the liver. In addition to /3-hydroxybutyrate and acetoacetate, the blood of diabetics also contains acetone, which results from the spontaneous decarboxylation of acetoacetate ... 

In fast white fibers, glycolysis catabolizes glucose. The relative lack of mitochondria in these fibers causes the white appearance. The rapid breakdown of glucose by anaerobic metabolism means that ATP is made rapidly. These muscles are used in rapid, short-duration movement and exhibit a fast twitch when electrically stimulated. The flight muscles of birds are of this type—remember that you find the white meat of a chicken on the breast. 

Pharmacokinetic processes are broadly defined as absorption, distribution, metabolism, and excretion, giving rise to the frequently used acronym — ADME. Each of these processes has a kinetic component and an extent component. The former refers to the rate of movement or how fast the process occurs over time, whereas the extent... 

Unlike mammals, which actively regulate their body temperature through metabolic activity, lizards are ectotherms—their body temperature depends on their surroundings. When splashed with cold water, a lizard s body simply gets colder. The drop in body temperature immobilizes the lizard because its movement depends on chemical reactions that occur within its muscles, and the rates of those reactions— how fast they occur—are highly sensitive to temperature. In other words, when the temperature drops, the reactions that produce movement in the lizard occur more slowly therefore, the movement itself... 

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